Will this Graphics card work with my system?

Hello everyone, I am in need for some much needed dire confirmation on if a graphics card will work in my system, I'll start by introducing the graphics cards: it's the XFX HD 6870. After much research I have found that is is probably the best graphics card I can get for under £150 (Literally what I googled a thousand times). I have only found out that the graphics card requires a minimum PSU of 500 watts, and as luch would have it, I fall short with only a 450 watt PSU.

XFX HD 6870: http://www.ebuyer.com/279585-xfx-hd-6870-900mhz-1gb-gdd...

Now more into my PSU, It's a XFX PRO450W, It's very reliable and I do not suffer from any problems, power wise.

XFX PRO450W: http://xfxforce.com/en-us/Products/Power-Supply/XFX/Pro...

Really my question is that will it work, I'm really dead set on getting this graphics card and I'm also really happy with the performance with my PSU and really don't want to change it as its only 4 Months old.

Another this people may fail to notice if I regret to mention is the fact the PSU come's with a single PCI-E 6 pin connector and the XFX HD 6870 requires two. I simply plan to purchase a dual 4 pin molex to 6 pin PCI-E adapter, is doing this recommended iof you fall short on 6 pin PCI-E connectors?

So once again, Do you think this graphics card will work with my PSU and is the use of a dual 4 pin molex to 6 pin PCI-E adapter good enough or does it cause problems?

Thanks